SUMMARY OF OBJECTIVES: To provide immunodeficient, a thymic nude mice, adequate facilities, and expertise for long-term studies of human tissue xenotransplants as the biological assay system for studying human carcinogenesis. GENERALLY: Provide a self-sustaining, nude mouse colony for Long-term studies of fresh human tissues, and/or in vitro induced transformation in human cells for in vivo expression and transplantation of malignancies in mice for cancer interruption studies. SPECIFICALLY: Provide as routine capability (1) 12 month survival studies of human tissues and cells transplanted subcutaneously as in vivo implants with viable epithelium and normal histology, in a self- sustaining, barrier colony accessible only by antibacterial personal showers and autoclaves for supplies; (2) Long-term survival studies of human organ tissue xenografts; (3) Long-term growth, proliferation, and tumorigenicity studies of cells for in vivo expression of preneoplastic and neoplastic transformation experimentally induced by selected chemical agents and genetic transfections. Materials Pick-up & delivery, Histopathology slide preparations and diagnoses, maintenance and expansion of the NCI-developed, dBASE-IBM PC colony data base, and veterinarian health care for breeders and experimental animals must support the continuing assay requirement of 10 scientists initiating an average of 50 new experiments, using 2,000+ mice/year.